Recent evidence suggests that, coincident with the AIDS epidemic, the incidence of severe infections and deaths due to bacterial infections has risen dramatically among intravenous drug users in New York City. The present study is designed to investigate the relationship between HIV infection and the occurrence and severity of two such infections; bacterial endocarditis, and bacteremia other than endocarditis. Specifically, the following objectives will be addressed: 1. Is there an increased prevalence of HIV seropositivity among drug users with acute infection compared to uninfected controls? Seropositivity rates will be compared for there groups of intravenous drug users; those with infective endocarditis, those with bacteremia other than endocarditis, and controls admitted for reasons unrelated to infection. 2. Is there a difference in the bacteriologic spectrum of infection seen among HIV seropositive drug users compared to those who are seronegative? The bacteriologic spectrum seen in HIV seropositive vs. HIV seronegative individuals with endocarditis and non-endocarditis bacteremia will be compared with that seen in seronegative patients. Each group of infected patients will be analyzed separate. 3. Is endocarditis or other bacteremia more severe in HIV seropositive vs. HIV seronegative intravenous drug users? Parameters of clinical severity of disease including presence of systemic hypotension and acidosis, need for intensive care admission, occurrence of pyogenic complications and mortality will be compared for seropositive vs. seronegative patients in each of the two groups of infected patients. 4. Is there a relationship between the clinical severity of these two infections and proposed clinical staging classifications for HIV disease? All study participants will have T-cell studies done. Using the same parameters of severity mentioned in objective 3 we will attempt to correlate course and outcome of acute infection with the proposed Walter Reed Staging Classification for HIV disease.